After the Long Term Evolution (LTE) system goes through a plurality of versions R8/9/10, the R11 technology is accurately studied in succession. At present, part of R8 products start to be gradually commercial, and product planning needs to be further performed for the R9 and R10.
After going through the R8 and R9 stages, many new characteristics are added in the R10 based on the R8 and R9, such as pilot frequency characteristics including Demodulation Reference Signal (DMRS) and Channel State Information Reference Signal (CSI-RS), and transmission and feedback characteristics including 8-antennae support and so on, and especially, in the enhanced Inter-Cell Interference Cancelling (eICIC) technology, the inter-cell interference avoidance technology is further considered based on the consideration of R8/9 Inter-Cell Interference Cancelling (ICIC). With regard to the technology of solving the inter-cell interference problem, the cell interference avoidance in a homogeneous network is mainly considered at an initial stage of R10, wherein the eICIC technology and the Coordinated Multi-Point (CoMP) technology are primarily considered. The CoMP, as the name implies, is various nodes coordinating to send data to one or multiple User Equipments (UE) in the same time frequency resource or different time frequency resources. With such technology, the inter-cell interference can be reduced, which enhances the cell edge throughput rate and extends the cell coverage. However, since it considers that more scenarios are introduced in a heterogeneous network at a later stage of the discussion, due to a complexity of the CoMP technology and a time limitation of the R10 discussion, a final decision is that additional CoMP standardization contents are not introduced in the R10 stage, but when the CSI-RS is designed, the design can be performed considering needs of the CoMP part, and thus the CoMP technology is not further discussed after the 60 bis conference.
In the initial stage namely a Study Item (SI) stage of the R11 discussion, a uniform evaluation architecture is mainly determined by planning scenarios and various transmission technologies of the CoMP, and it is proved that a significant performance gain can be obtained with the CoMP technology through 2 stages of CoMP evaluation. In the CoMP SI conclusion that is completed recently, it is required to carry out further study on Joint Transmission (JT), Dynamic Point Selection (DPS) with/without muting, Coordinated Scheduling (CS) with/without muting and Coordinated Beamforming (CB) in the CoMP technology.
Before studying various technologies of the CoMP, what need to be firstly considered are differences possessed by the CoMP technology relative to the R8/9/10 technologies, wherein it includes how a control signaling of the CoMP supports a notification of the CoMP measurement set, how it supports demands of various transmission technologies of the CoMP, and how the UE measures and reports Channel State Information (CSI) of a plurality of nodes and so on. Wherein, how a network side uses a downlink control signaling to notify the UE to correctly receive and detect service data is one of primary problems required to be solved in the CoMP technology. The CoMP requires a plurality of nodes coordinating to send downlink service data or control channels to one UE, thus the UE needs to know configuration information of different nodes, and with regard to a traditional R8/R9/10 UE, it only accesses a primary serving cell during the initial access and only obtains system information of the primary serving cell, thus, when other nodes transmit data to the UE, a situation of incorrectly receiving the data may occur since system information of the relevant nodes are unknown.
In the latest R11 discussion process, a concept of CSI process is raised, one CSI process is related to one channel measurement part and one interference measurement part, one CSI process corresponds to one channel measurement assumption and one interference measurement assumption, and one CSI process requires a terminal feeding back one corresponding CSI. For a CoMP system, since each terminal needs to feed back CSIs of multiple Transmitting Points (TP), and scenarios of the CoMP and Carrier Aggregation (CA) are considered, the amount of CSIs required to be fed back by one terminal is very large, thus a collision problem will be caused at this point. For the CA, if a certain CSI element or a plurality of CSI elements have a collision between the CSI processes, which CSI is discarded is decided according to a priority of feedback type and carrier configuration. At this point, since different carriers require to feed back different CSIs, and the different carriers are independent with each other, all discards do not have a big impact on performance of the CA scenario. However, for the CoMP scenario, discarding CSIs will cause a limitation on the CoMP scheduling, thereby influencing the obtainment of the CoMP performance gain. If a scenario of combining the CoMP and the CA is considered, in a scenario where more CSIS are discarded, the CoMP performance gain of each carrier will be influenced. Therefore, it is required to further consider an optimization problem of the collision in the CoMP scenario, and especially, to consider a problem of how to avoid discarding when the collision occurs.